Hydrogenation and distillation of lubricating oils



De@ 15, 1959 H. BEUTHER ErAL HYDROGENATION AND DISTILLATION OF LUBRICATING OILS Filed NOV. 15. 1956 BY RODNE Y E PE'E/SN INVENTORS HARo/ D Eur//ER ALFREo M. #EN E United States Patent O HYDROGENATIN AND DISTILLATION OF LUBRICATING OES Harold Beuther, Penn Township, Allegheny County, Al-

fred M. Henke, Springdale, and Rodney E. Peterson, Oakmont, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Application November 15, 1956, Serial No. 622,312

2 Claims. (Cl. 208-57) This invention relates to improved procedure for preparation of lubricating oils. It has been known to subject lubricating oil stocks to treatment with hydrogen in order to purify them or convert them into oils having improved lubricating properties. These known procedures have certain disadvantages. For instance, some of these procedures have resulted in poor yields of lubricating oil. Others have resulted in lubricating oils of relatively low quality as cornpared with known methods of refining lubricating oils. This invention has for its object to provide improved procedure for preparing lubricating oils. Another object is to provide procedure for preparing lubricating oils whereby the foregoing diiculties may be overcome. A

.still further object is to provide improved procedure for preparing lubricating oils by treatment with vhydrogen whereby higher yields may be obtained. A still further object is to provide improved procedure for preparing ylubricating oils by treatment with hydrogen which will result in high quality lubricating oils. Other objects will appear hereinafter.

These and other objects are accomplished by our invention which comprises subjecting a crude lubricating oil stock which contains asphaltic materials and wax to vacuum distillation to separate an unpressable distillate and au undistilled residue which contains asphaltic materials. The undistilled residue is then deasphalted. The deasphalted portion is then combined with the unpressable distillate and the mixture is contacted with hydrogen in the presence of a catalyst selected from a group consisting of sulldes of a metal of the left-hand column of group Vl metals of the periodic system and a mixture of va sulde of a metal of the left-hand column of group VI metals of the periodic system with a suldeof a metal of the iron group. This contacting takes place at a pressure between about 2000 and 4000 p.s.i., at a temperature between about 685 and 750 F., at a space velocity between about 0.25 and 2, the specific reaction conditions being selected within these limits to obtain extensive hydrogenation of aromatic hydrocarbons into naphthenic hydrocarbons. The hydrogen treated prodyuct is dewaxed. The dewaxed hydrogen treated product is subjected to vacuum distillation to separate a plurality of lubricating oil fractions having the desired SAE viscosity. These fractions are then subjected to treatment with hydrogen in the presence of acatalyst selected from the group consisting of a sulde of `a metal of the lefthand column group VI metals of the periodic system, atsuliide of a metal of the left-hand column group VI metals of the periodic system mixed with a sulde of a metal of the iron group, an oxide of a metal of the lefthand column group VI metals of the periodic system, an oxide of `a metal of the iron group and mixtures of an oxide of the left-hand column group VI metals of the periodic system with an oxide of a metal of the iron group. This hydrogen treatment is carried out at a pressure between about 500 and 1000 p.s.i., a temperature between about 500 and 600 F. and at a space'velocity 2 between about 0.5 and 4, the specific conditions selected within these limits being such that substantially all olens, diolens and color bodies are hydrogenated without causing substantial formation of lower boiling hydrocarbons by thermal-cracking or hydrocracking.

In the following examples and description we have set forth several of the preferred embodiments of our invention, but it is to be understood that they are given by way of illustration and not in limitation thereof.

The charge stock to the first hydrogenation treatment may be any lubricating oil stock such as a lubricating oil distillate, vacuum reduced crude, cylinder oil stock, etc. It may be derived from any crude which contains lubricating oil components such as crudes derived from Pennsylvania, Texas, California, Venezuela, or Kuwait. While a charge stock may be employed which contains only a single lubricating oil viscosity grade, we prefer to employ a charge stock which contains a plurality of lubricating oil viscosity grades or a wide range lubricating oil stock. We also prefer to utilize a charge stock to the first hydrogen treatment which has been deasphalted or which is relatively free of asphalt. This is desirable since the asphalt will not only lower the life of the catalyst by increasing the rate of coke deposition but also produces products of lower V.l. Any lube oil charge stock may be used which has a Saybolt viscosity at F. lof between about 150 and 3000. A charge stock having a viscosity within this range usually need not be treated to remove any of its components prior to the first hydrogen treatment unless it contains large amounts of asphaltic materials as discussed above. Thus it is not necessary to solvent extract the charge stock with materials such as phenols, furfural, etc. As a matter of fact it is a distinct advantage of the present invention that materials which are removed by such solvents are converted in the iirst stage of the process into valuable lubricating oil components. The charge stock may be treated to completely or partially remove wax components prior to treatment in the rst stage. However, it is an advantage of the present invention, except with charge stocks which contain excessively large amounts of wax, that dewaxing may be applied to the charge stock after theufirst'hydrogenatiou treatment. Thus it has been found thatseparation of the wax components is facilitated by the hydrogen treatment. This, apparently, is due to the presence of materials formed during the hydrogen treatment. This mode of operation is especially useful in connection with unpressable lube oil fractions and residuums. Wax-like materials are not formed to any substantial extent during the hydrogen treatment so that if a charge stock containing no wax components or no harmful amounts of wax components is employed, it will be unnecessary to dewax after the hydrogen treatment. However, with a charge stock which contains undesirable amounts of wax, it is advisable to dewax in known mannerV either before or after, and preferably after, the hydrogen treatment. Such dewaxing may be accomplished by any conventional procedure such as precipitating the wax in the presence of a mixture of benzene and acetone, a mixture of toluene `and methyl ethyl ketone or cooling followed by filtering in a filter press. It is also advantageous, although not necessary, to degas the charge stock to the first stage hydrogen treatment in order to remove absorbed oxygen and water. This may be accomplished by subjecting it to reduced pressure,

The conditions for the first hydrogen treatment are selected within the above described ranges to result in hydrogenation of the aromatic hydrocarbons into naphthenic hydrocarbons. As a general rule temperature and space velocity are interchangeable. Thus the extent of hydrogenation of the aromatics using a lower space velocity and a lower temperature may be equal 'to thatchtained by using a higher space velocity with a higher temperature. Alternatively an equal degree of hydrogenation of aromatics may be obtained by using a fixed temperature and a lower space velocity or by using a fixed space velocity and a higher temperature. The conditions should be selected within the ranges described above to obtain hydrogenation of aromatics without excessive hydrocracking into lower boiling products. However, the hydrogenation of aromatics cannot be accomplished without some hydrocracking into lower boiling components. These lower boiling components in many cases have valuable lubricating oil properties when subjected to the subsequent procedures of our invention. For optimum results we prefer to employ in the first stage hydrogen treatment a pressure between about 2000 and 4000p.s.i., a temperature between about 685 and 750 F. and a space velocity between about 0.25 and 2. The hydrogen is recycled in amounts between about 1000and 20,000 s.c.f. per barrel of charge and preferably between about 2000 and 10,000 s.c.f. per barrel. Y 1

The product from the first hydrogenation treatment, after dewaxing, if this is advisable, is then subjected to vacuum distillation to separate the desired lubricating oil viscosity grades. This distillation also results in removal of fractions formed during the first stage hydrogen treatment which have little or no lubricating oil value. This vacuum distillation may be carried out in known manner. Thus any conventional vacuum or steam distillation used to obtain lubricating oil fractions may be employed. The pressure or partial pressure of the oil vapors (steam added) utilized in the vacuum or steam distillation is usually between about 1.0 and 20.0 mm. Hg. No matter what lubricating oil charge stock is employed in the first stage hydrogenation, a plurality of viscosity grade lubricating oils will be present in the product from the rst stage and may be removed as separate fractions during the vacuum distillation.

In the event that sulfur-containing lubricating oil charge stocks are employed, the sulfur compounds will be converted to a large extent into hydrogen sulfiderduring the first stage hydrogen treatment. During the vacuum distillation any small amount of hydrogen sulde remaining dissolved in the lube oil fractions will be removed as a gas by the vacuum producing system.

The lubricating oil fraction or fractions separated in the vacuum distillation step is or are then subjected to a second treatment with hydrogen. Since the first hydrogen treatment converts aromatic hydrocarbons to lube oil components, it is unnecessary to remove them as by solvent extraction. Therefore, with the exception of wax removal, there need be no treatment between the rst hydrogen stage and the vacuum distillation and no treatment of any kind between the vacuum distillation and the second hydrogen treatment. The conditions utilized in the second hydrogenation step are selected within the ranges described above to obtain substantially no hydrocracking or conversion into lower boiling products. Y The objective is to hydrogenate olefins, diolefins and color bodies without thermal or other decomposition. We pref fer to employ a pressure between about 500 to 1000 p.s.i., a temperature between about 500 to 600 F. and a space velocity between about 0.5 and 4 in the second hydrogenation treatment. Hydrogen is recycled at the rate of between about 300 and 8000 s.c.f, per barrel and preferably between about 500 and 2000 s.c.f. per barrel of oil. As with the first hydrogenation treatment, temperature and space velocity are interchangeable in obtaining the desired result, i.e. hydrogenation of olefins, diolefins and color bodies with minimum or no hydrocracking.

Both hydrogenation stages may be carried out by passing the charge stock either upwardly or downwardly through a fixed bed of the catalyst. If desired, the catalyst may be suspended as nely divided particles in the lubricating oil stock and passed through the reactor. This has the disadvantage that filtration to remove catal lyst is required. We prefer to employ a xed bedof catalyst and up-flow of the charge stock through the catalyst bed.

Hydrogenation catalysts which promote hydrogenation of aromatic hydrocarbons to a high degree are well known. Any such catalyst having a high activity for this reaction may be employed in the first hydrogen treatment. Suitable catalysts are suldes of metals of the lefthand column of group VI metals of the periodic system either alone or mixed with sulfides of metals of the iron group. Specific examples of such catalysts are tungsten disulfide, a mixture of tungstenrand nickel sulfides, and a mixture of tungsten and cobalt sulfides. We prefer to employ a mixture of tungsten and nickel suldes in which the nickel to tungsten atomic ratio is between about 2 and 4. A similar atomic ratio for the tungsten and cobalt sulde mixture is desirable. These catalysts may be supported on porous carriers such as activated alumina, silica alumina, etc. However, we prefer to utilize these catalysts without supports. Thus the active components may be pelleted or otherwise shaped into the desired catalyst size and used as a catalyst in this form.

The catalyst used in the second stage hydrogenation may be any hydrogenation catalyst having a high activity for hydrogenation of oleiins. Such catalysts are well known. Examples of suitable catalysts for this treatment are the sulfide catalysts used in the rst stage of hydrogen treatment, oxides of metals of group VI, left-hand column of the periodic table, oxides of metals of the iron group and mixtures of oxides of metals of group VI, left-hand column with oxides of metals of the iron group. We prefer to employ as catalysts mixtures of cobalt and molybdenum oxides, nickel and molybdenum oxides, plat` inum or a mixture of nickel and tungsten oxides. These catalysts are preferably supported on porous carriers such.

as activated alumina, Alfrax and kieselguhr, magnesia" or pumice. The catalysts mentioned for the first and second stage hydrogen treatments have a long life. This is especially true of the sulfide and cobalt-molybdenum catalysts which may be used for periods of several months to several years. l

In the accompanying drawing we have illustrated diagrammatically apparatus in which our process may be carried out.

Referring to the drawing, numeral 2 indicates a vacuum still into which a lubricating oil stock such as a topped crude is introduced through conduit 4. The topped crude is distilled to remove three distillates and a bottoms fracf tion. The first distillate constituting heavy gas oil is re moved through conduit 6. Pressable distillate is removed through conduit 8 yand may be used to prepare a lubricating oil in conventional manner. On the other hand this pressable distillate may be treated in accordance with the invention either with or without filter pressing to rcmove wax. Unpressable distillate is removed through conduit 10 and a bottoms fraction is removed through conduit 12.

This bottoms fraction is treated to remove. asphaltic materials in unit 14. This may be accomplished in known manner by precipitation in the presence of material such as propane introduced through conduit 15. Precipitated asphaltic substances are removed through conduit 17. The bottoms fraction freed of asphalt fiows through conduit 16 and is combined with the unpressable distillate flowing through conduit 10. A mixture of fresh hydrogen and recycle hydrogen flowing through conduit 18 is combined with the mixture of deasphalted bottoms and unpressable distillate. This mixture is heated to approximately reaction temperature in heater 20 and is then introduced by way of conduit 22 into reactor 24. This reactor contains a fixed bed of catalyst active for hydrogenation of aromatic hydrocarbons and as the mixture of hydrogen and lube oil charge stock ows therethrough,

, it contacts the catalyst and the reactions described above AAM The eluent ows through conduit 25 into high pressure separator 26 where hydrogen is separated and recirculated via conduits 28, 30 and 18. A small amount of make-up hydrogen is introduced through conduit 32. The liquid from high pressure separator 26 flows through conduit 34 into low pressure separator 36 where gases such as methane, hydrogen sulde, etc. formed during the reaction and soluble in the lube oil stock at high pressure are given olf at the lower pressure. These gases are removed through conduit 38. The lube oil stock then flows through conduit 40 into dewaxing unit 42 where the wax is separated and removed through conduit 44 as a result of precipitation in the presence of a solvent introduced through conduit 46. The solvent and oil mixture from dewaxer 42 flows through conduit 48 into stripper 50 where the solvent is removed by steam introduced through conduit 52. The mixture of steam and solvent is removed through conduit 54 and sent to a solvent recovery system (not shown). The lube oil stock then flows through con-` duit 56 into still 58 Where the lube oil stock is subjected to distillation under vacuum. A light distillate is removed through conduit 60 and may be used as light lubricant or turbine oils, etc. Three lube oil fractions of progressively increasing viscosity are removed through conduits 62, 64 and 66. Of course the number of lube oil fractions removed will vary depending upon the charge stock and the number of fractions desired. These lube oil fractions are sent to storage vessels 68, 70 and 72 respectively.

The lube oil fractions thus separated are then separately subjected to the second hydrogenation treatment. In the event that the lightest lube fraction is to be treated first, valve 74 is opened and the light lube oil fraction ilows through conduit 76 into heater 78 after mixing with fresh hydrogen introduced through conduit 80 and recycle hydrogen introduced through conduit 82. The mixture of light lube oil and hydrogen is heated to about reaction temperature in heater 78 and then ows upwardly through reactor 84. Reactor 84 contains a catalyst active for hydrogenation of olefins. Here the reactions described above take place in the presence of a fixed bed of hydrogenation catalyst. Since the catalysts which promote hydrogenation of olefins also promote hydrogenation of diolens and color bodies, these materials are also converted or removed during the second stage hydrogenation treatment.

The reaction products are removed through conduit 86 and flow into high pressure separator 88 where the hydrogen is separated and recycled through conduit 90. The lube oil then flows through conduit 92 into low pressure separator 94 where any small amount of light gases present are removed through conduit 96. The finished lube oil product is then removed through conduit 98.

The individual lube fractions n reservoirs 70 and 72 are individually treated in the same manner as described in connection with the lighter lube oil fraction in reservoir 68. Alternatively if it is desired to produce the final lube oil fractions simultaneously, a separate reaction systern for the final hydrogenation treatment may be provided for each of these lube oil fractions. While we have described the operation with three lube oil fractions, a larger or smaller number of fractions may be treated in the same manner. In some cases the lighter lube fractions are more refractory than the heavier fractions and where they are treated inthe first stage in admixture with heavier fractions, it may be advantageous to partially recycle them from vacuum still 58 to the first hydrogen treatment in reactor 24. Alternatively the treatment in the first stage reactor 24 may be adjusted within the more severe portions of the reaction ranges disclosed above to result in complete conversion to lighter lube oil portions. This may result in a somewhat greater conversion of heavier lube oil into lighter ends but they will be removed in the subsequent distillation.

6 EXAMPLE A blend of 67 percent by volume Ordovician unpressable distillate and 33 percent by volume Ordovician deasphalted residuum ywas subjected to treatment in a first hydrogen treating stage at a temperature of 705 tov .pressure of 5 mm. Hg Iand a light fraction constituting 14 percent (based on the original charge) and boiling between 450 and 725 P. was removed and discarded.

' Three lubricating oil fractions having viscosities of SAE 10,'25 and 50 oils were removed in amounts of 28 percent, 27 percent and 18 percent respectively (based on the amount of the original charge stock to the rst hydrogent treatment). The properties of the charge stock, of the product from the first hydrogen treatment and of the product from the dewaxing are given in Table I.

The SAE 10, 25 and 50 fractions separated as described in the preceding paragraph were then separately subjected to treatment with hydrogen in the presence of a cobalt molybdate catalyst supported on alumina. The temperature in each of these hydrogenations was 525 F., the pressure 1000 p.s.i.g., the space velocity 1, and hydrogen was circulated at a rate of 2500 s.c.f. per barrel. The properties of the charged fractions to the second hydrogenation and of the products formed in the second hydrogenation are given in Table II.

Table I After First After De- Charge Hydrogen Waxing Treatment Gravity. API 25. 1 32. 2 31. 4 Viscosity:

100 65 155 203 10 72. 8 46 48 Viscosity Index 99 135 125 umher. 14.1 2. 1 3. 3 Percent Aromat 14. 6 3. 0 4. 0 olor -3.5 (dil.) 1.0 1.75 Carbon Res.-- 0,7 0.01 0.01 Neut. No 0. 04 0.01 0.01 Pour Point, degrees +90 0 Yield (based on original oil), percent 99, 6 87 Table II SAE 10 SAE 25 SAE 50 Before After Before After Before After Gravity, API- 31. 6 31. 7 31. 1 31. 2 29. 1 29.3 Vlscosrty:

100 155 155 317 317 l, 180 l, 180 2l0 43. 8 43. 8 55. 3 55.3 105. 1 105. 1 Viscosity In 111 111 110 110 107 107 Ig Number 3.4 2. 6 3. 7 2.3 3. 4 1. 9 Percent Aromatics.- 4. 5 4. 5 3. 5 3. 5 1. 0 1. 0 Olor 1. 75 1 2. 25 1 3. 25 2. 00

(dil.) Pou Point d es 0. 0g 0. 0(1) 0.401 0.12 0. 03 r eg're 5 5 5 Carbon Res 0. 01 0. 01 0. 01 0.01 0.410 0753 We claim:

1. The process for preparing an improved lubricating oil from a crude lubricating oil stock which contains asphaltic materials and wax which comprises in combination subjecting the lubricating oil stock to vacuum distillation to separate an unpressable distillate and an undistilled residue which contains asphaltic materials, deasphaltng the residue, combining the deasphalted residue with the unpressable distillate, Icontacting the combination of deasphalted residue and unpressable distillate with hydrogen in the presence of a catalyst selectedfrom the group consisting of a sulfide of a metal of the lefthand column of group VI metals of the periodic system and a mixture of a sulde of a metal of the left-hand column group VI metals of the periodic system with a sulfide of a metal of the iron group at a pressure between about 2000 and 4000 p.s.i., at a temperature between about 685 and 750 F., `at a space velocity between about 0.25 and 2, the specific reaction conditions that are used being selected within these limits to result in extensive hydrogenation of aromatic hydrocarbons into naphthenic hydrocarbons, dewaxing the hydrogen treated product, subjecting the hydrogen treated and dewaxed product to vacuum distillation to separate a plurality of lubricating oil fractions having the desired SAE viscosity and separately subjecting these fractions to treatment with hydrogen in the presence of a catalyst selected from the group consisting of a sulfide of a metal of the left-hand volumn, group VI metals of the periodic system, a sulfide of a metal of the left-hand column group VI metals of the periodic system mixed with a sulfide of a metal of the iron group, an oxide of a metal of the left-hand column group VI metals of the periodic sytem, an oxide of a metal of the iron group and mixtures of an oxide of the left-hand column group VI metals of the periodic system with an oxide of a metal of the iron group at a pressure between about 500 and 1000 p.s.i., a temperature between about 500 and 600 F. and a space velocity between about `0.5

aud 4, said conditions being selected within these limitsY so that substantially all oleins, diolefins and color bodies are hydrogenated without causing substantial formation of lower boiling hydrocarbons by a member of the group consisting of thermal cracking and hydrocracking.

2. The process for preparing an improved lubricating oil from a crude lubricating oil stock which contains asphaltic materials and wax which comprises in cornbination subjecting the lubricating oil stock to vacuum distillation to separate an unpressable distillate and an undistilled residue which contains asphaltic materials, deasphalting the residue, combining the deasphalted residue with the unpressable distillate, contacting the combina--l tion of deasphalted residue and unpressable distillate with hydrogen in the presence of a nickel sulfide-tungsten sulfide catalyst at a pressure between about 2000 and 4000 p.s.i., at a temperature between about 685 and 750 F., at a space velocity between about 0.25 and 2, the specific reaction conditions that are used being selected within these limits to result in extensive hydrogenation of aromatic hydrocarbons into naphthenic hydrocarbons, dewaxing the hydrogen treated product, subjecting the hydrogen treated and dewaxed product to vacuum distillation to separate a plurality of lubricating oil fractions having the desired SAE viscosity and sep arately subjecting these fractions to treatment with hydrogen in the presence of cobalt oxide-molybdenum oxide catalyst at a pressure between about 500 and 1000 p.s.i.,

' a temperature between about 500 and 600 F. and a space velocity between about 0.5 and 4, said conditions being selected within these limits so rthat substantially all olelins, dioletins and color bodies are hydrogenated without causing substantial formation of lower boiling hydrocarbons by a member of the group consisting of thermal cracking and hydrocracking.

References Cited in the tile of this patent UNITED STATES PATENTS 2,459,465 Smith Ian. 18, 1949 2,706,167 Harper et al Apr. 12, 1955 2,779,713 Cole et al Jan. 29, 1957 2,790,754 Johnston et al. Apr. 30, 1957 OTHER REFERENCES Sachanen: Conversion of Petroleum, second edition, Reinhold Publishing Corp., N.Y., 1948, pp. 386-388. 

1. THE PROCESS FOR PREPARING AN IMPROVED LUBRICATING OIL FROM A CRUDE LUBRICATING OIL STOCK WHICH CONTAINS ASPHALTIC MATERIALS AND WAX WHICH COMPRISES IN COMBINATION SUBJECTING THE LUBRICATING OIL STOCK TO VACUUM DISTILLATION TO SEPARATE AN UNPRESSABLE DISTILLATE AND AN UNDISTILLED RESIDUE WHICH CONTAINS ASPHALTIC MATERIALS, DE ASPHALTING THE RESIDUE, COMBINING THE DEASPHALTED RESIDUE WITH THE UNPRESSABLE DISTILLATE, CONTACTING THE COMBINATION OF DEASPHALTED RESIDUE AND UMPRESSABLE DISTILLATE WITH HYDROGEN IN THE PRESENCE OF A CATALYST SELECTED FROM THE GROUP CONSISTING OF A SULFIDE OF A METAL OF THE LEFTHAND COLUMN OF GROUP VI METALS OF THE PERIODIC SYSTEM AND A MIXTURE OF A SULFIDE OF A METAL OF THE PERIODIC SYSTEM COLUMN GROUP VI METALS OF THE PERIODIC SYSTEM WITH A SULFIDE OF A METAL OF THE ION GROUP AT A PRESSURE BETWEEN ABOUT 2000 AND 4000 P.S.I., AT A TEMPERATURE BETWEEN ABOUT 685* AND 750* F., AT A SPACE VELOCITY BETWEEN ABOUT 0.25 AND 2, THE SPECIFIC REACTION CONDITIONS THAT ARE USED BEING SELECTED WITHIN THESE LIMITS TO RESULT IN EXTENSIVE HYDROGENATION OF AROMATIC HYDROCARBONS INTO NAPHTHENIC HYDROCARBONS, DEWAXING THE HYDROGEN TREATED PRODUCT, SUBJECTING THE HYDROGEN TREATED AND DEWAXED PRODUCT TO VACUUM DISTILLATION TO SEPARATE A PLURALITY OF LUBRICATING OIL FRACTIONS HAVING THE DESIRED SAE VISCOSITY AND SEPARATELY SUBJECTING THESE FRACTIONS TO TREATMENT WITH HYDROGEN IN THE PRESENCE OF A CATALYST SELECTED FROM THE GROUP CONSISTING OF A SULFIDE OF A METAL OF THE LEFT-HAND VOLUMN, GROUP VI METALS OF THE PERIODIC SYSTEM, A SULFIDE OF A METAL OF THE LEFT-HAND COLUMN GROUP VI METALS OF THE PERIODIC SYSTEM MIXED WITH A SULFIDE OF A METAL OF THE IRON GROUP, AND OXIDE OF A METAL OF THE LEFT-HAND COLUMN GROUP VI METALS OF THE PERIDOIC SYSTEM, AND OXIDE OF A METAL OF THE IRON GROUP AND MIXTURES OF AN OXIDE OF THE LEFT-HAND COLUMN GROUP VI METALS OF THE PERIODIC SYSTEM WITH AN OXIDE OF A METAL OF THE IRON GROUP AT A PRESSURE BETWEEN ABOUT 500 AND 1000 P.S.S., A TEMPERATURE BETWEEN ABOUT 500* AND 600* F. AND A SPACE VELOCITY BETWEEN ABOUT 0.5 AND 4, SAID CONDITIONS BEING SELECTED WITHIN THESE LIMITS SO THAT SUBSTANTIALLY ALL OLEFINS, DIOLEFINS AND COLOR BODIES ARE HYDROGENATED WITHOUT CAUSING SUBSTANTIAL FORMATION OF LOWER BOILING HYDROCARBONS BY A MEMBER OF THE GROUP CONSISTING OF THERMAL CRACKING AND HYDROCRACKING. 